This project uses electron microscopy, histochemistry, and autoradiography to study cartilage proteoglycans and their relationship to collagen in cartilage matrix. We are exploring several systems. Samples of bovine nasal septum that have been treated with enzymes or proteoglycan-extracting reagents are processed for high resolution electron microscopy to give further information on collagen structure, on the representation of proteoglycans by matrix granules, and on the relationship of proteoglycans to collagen. Purified proteoglycan and Type II collagen have been isolated from the Swarm rat chondrosarcoma; the addition of the proteoglycan to soluble collagen solutions affects collagen fibril formation, giving a system for studying proteoglycan collagen interactions in vitro.